Magnetic recording hard disk drives are widely used in computers and data processing systems for storing information in digital form. These disk drives commonly include one or more rotating storage disks and one or more head arm assemblies. Each storage disk typically includes a plurality of tracks. Each head arm assembly includes one or more arm beams (sometimes referred to as actuator arms) and one or more head gimbal assemblies. Each head gimbal assembly includes a load beam, a base plate that secures the load beam to the arm beam, a slider, a flexure that connects the slider, and electrical conductors. The slider includes a data transducer and an air bearing surface.
The rotation of the storage disk causes the slider to ride on an air bearing a distance “h” from the storage disk. The distance “h” is referred to as the “flying height” of the slider and represents the position that the slider occupies when the storage disk is rotating during normal operation of the disk drive. Because of the cantilever spring action of the load beam, a force, commonly referred to as the gram load, is transmitted to the slider and is exerted on the air bearing. The distance between the air bearing surface of the slider and the surface of the actuator arm connected to the suspension is commonly referred to as a Z height. The pitch of the slider is commonly referred to as the pitch static attitude (PSA) of the slider and the horizontal roll of the slider is commonly referred to as the roll static attitude (RSA) of the slider.
The need for increased storage capacity, compact construction, and reduced cost has led to disk drives having fewer storage disks, with each storage disk having increased track density. As track density increases, it is necessary to decrease the flying height of the slider, have tighter control on the flying height and maintain the flying height within a certain range. For example, if the flying height is too high, the quality of the data transferred to and from the storage disk is degraded. Alternately, if the flying height is too low, the slider can contact the storage disk during operation. This can damage the slider, the storage disk, and/or may generate particles that would drastically shorten the life of the drive. As a result thereof, accurately controlling the flying height of the slider is critical to the accurate transfer and/or retrieval of information from the storage disk.
The flying height of the slider is influenced by a number of factors, including the rotation speed of the storage disk, the design of the air bearing surface of the slider, the pitch static attitude, the roll static attitude, the gram load, the Z height, and temperature within the drive. For example, as temperature changes, the shape of the slider changes. In some drives, this change in shape causes the flying height of the slider to be greater at a lower temperature than the flying height is at a higher temperature.
The temperature within the drive is primarily influenced by the environmental temperature, e.g. the room temperature, and the usage of the drive. As an example, during operation, the temperature within the drive can be approximately 5° C. Alternately, with a different room temperature and/or under different operating conditions, the temperature within the drive can be approximately 25° C. In certain drives, the flying height of the slider in the drive at 5° C. is substantially higher than the flying height of a drive at 25° C.
As a result thereof, the flying height of the slider at lower temperatures can be too high and the flying height of the slider at higher temperatures can be too low. This limits the range of temperatures that the drive can accurately and safely operate.
In light of the above, the need exists for a way to maintain the flying height within a desirable range over a relatively large temperature range, including relatively low temperatures and relatively high temperatures. Yet another need exists to provide a way to control the gram load at various temperatures. Another need exists to provide a disk drive having improved performance reliability when exposed to a wide range of environmental conditions.